Hello guys,
I'm not an expert of 3d printing and also I'haven't a good knowledge of 3d modelling.
As I work as an archaeologist I need to reproduce some small objects like ancient coins to make plastic replicas.

Can you explain to me how to do a 3d .stl model from an image in .jpg or .bmp (in black and white of course) ? Are there some freeware software to make this operation?

Thanks for your support.
I did this operation on the online creator, but the result is very bad and I don't belive that it would be possible to print a 3d object from that .stl ...can you suggest me anothe solution to fix this problem?

Another way would be to use blender, it's been a while since I did it though, and I wouldn't say that I'd be able to create a properly scaled model myself. You may want to check out the Modeler Needed section to find someone that can help model your coins.

I learned a long time ago the wisest thing I can do is be on my own side, be an advocate for myself and others like me. -Maya Angelou
michael@shapeways.com Community Advocate

Another way would be to use blender, it's been a while since I did it though, and I wouldn't say that I'd be able to create a properly scaled model myself. You may want to check out the Modeler Needed section to find someone that can help model your coins.